Conventional semiconductor device fabrication usually entails fabrication of thin film devices on a substrate. Device thicknesses are typically on the order of 1-10 microns, while the substrate thickness is often 500 microns thick. Thus the cost of the substrate can be a significant factor for semiconductor devices. Epitaxial liftoff processes have been considered to alleviate this issue, where a thin layer of material including the fabricated devices is removed from the substrate, thereby enabling reuse of the substrate. For example, a sacrificial layer can be disposed between the device layer and the rest of the substrate. Etching of such a sacrificial layer with an etchant that etches the sacrificial layer but not the substrate or device layers can provide the desired liftoff of the device layers. However, such selective etching can be difficult to carry out in practice. Accordingly, it would be an advance in the art to provide improved epitaxial liftoff.